DUGi

Practical Aspects of Compositional Data Analysis using Regional Geochemical Survey Data

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@2072@@273431

Government geological surveys and mineral exploration companies collect large amounts of geochemicaldata, which are used in search for mineral commodities or for determining environmentaldisturbances. These surveys consist of many thousands of samples (observations) with as many as50 elements determined for each. Because the nature of the data is compositional, they must betreated according the protocols established by John Aitchison and others. This contribution detailsan approach based on the application of the alr, clr and ilr transforms for process discovery and validation.Issues of around the treatment of zeros and/or missing values are complicated due to thestoichiometric nature of the data. Case studies are presented where the use of logratio transformsand the estimation of replacement values for missing data are considered in the context of stoichiometricconstraints

Universitat de Girona. Departament d’Informàtica i Matemàtica Aplicada